The inner layer of the cornea is a single layer of neural crest-derived endothelial cells (CECs), which form a barrier between the cornea and the aqueous humor and transport water from the corneal stroma. CEC loss can result from eye injuries, complications from cataract surgery (pseudophakic bullous keratopathy (PBK) or aphakic bullous keratopathy (ABK)), and in an inherited condition known as Fuchs dystrophy.
These cells do not divide during adult life. Rather, existing CECs simply spread to compensate for loss or damage. When this spreading is inadequate, vision-impairing corneal opacity results.
Traditional treatment for CEC loss or damage is penetrating keratoplasty (PK), in which a full thickness cadaveric cornea is transplanted onto a recipient eye. However, a procedure known as DSEK (Descemet's Stripping and Endothelial Keratectomy) may be an option in some cases in which the corneal stroma is not scarred. In this procedure, CECs and their underlying basement membrane (Descemet's membrane) are physically removed from the recipient, and only the inner portion of a donor cadaveric cornea, including intact CECs, is transferred to the recipient eye.
More recently, the DMEK procedure (Descemet's Membrane Endothelial Keratoplasty) has been developed, in which the donor cadaveric tissue consists only of Descemet's membrane and CEC layers. Cultured CECs on synthetic films is also under study. These techniques are intended to improve the surgery by eliminating the presence of the posterior stromal tissue from the tissue graft containing CECs. Problems encountered from the stromal thickness include unpredictable refractive error, which may require the patient to wear thick glasses for correction. Presence of the stroma can also create interface haze or scarring. In addition, DMEK may minimize crowding of the anterior chamber to allow future procedures if needed (e.g., anterior chamber intraocular lens and tube shunt).
However, more options are needed to provide suitable alternative tissue sources for the restoration of the corneal endothelial cell layer, as well as the creation or restoration of the endothelial layer of other tissues.